What are the x and y axis for on a bar graph?

One axis contains the data sequence, whether categories, time, etc.

The other axis is used to represent the magnitude of each datum in the sequence.

For example, a bar graph of annual rainfall over 10 years from 2000-2009 might have an X axis labeled for each year and a Y axis indicating inches of rain fall.

The bars in the graph would then stretch up over each year value to the level on the Y axis representing the amount of rain that fell that year.